Smokey Yunick developed power brakes using residual power steering pressure about 50 years or more ago but NASCAR refused permission to use it. He did use it on Indy cars where the rule book was much thinner.
Edit - He first used it in 1959 on the works cars he built for Pontiac. They had variable ratio power steering which was also a Smokey invention. Drum brakes as Nascar did not approve discs until 1971. Nascar told the team to take this stuff off. Driver, Fireball Roberts did not want the innovations until he ran a race with the PS and brakes. Fireball was alleged to have gone looking for Nascar tech manager with malice aforethought armed with the removed brake unit to feloniously insert or bash the techies with. Smokey actually did assault Joe Hunt at Indy with a faulty Joe Hunt magneto. Belted him in the head with the faulty unit. These were more robust times.
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